The present invention relates in general terms to motor vehicle headlights.
There is at the present time a tendency to mount the lamp of such a headlight in its reflector in a generally transverse orientation, which may typically be either vertical or lateral, with respect to the optical axis of the reflector which defines the general direction taken by the beam emitted by the light. Such an arrangement has various advantages, in particular a reduction in the axial size of the headlight, because there is no need to provide any free space behind the latter to enable the lamp to be replaced. In addition, the lamp is made more accessible.
A further advantage of such an arrangement is that the base region of the reflector, which is traditionally occupied by the lamp hole through which the lamp is fitted axially into the reflector, is in this case available to play a part in the formation of the beam. This enables a more intense beam to be obtained.
However, the fact that the base region of the reflector plays a part in the formation of the beam gives rise to another difficulty. This is that the rays which are emitted by the lamp towards the base of the reflector are reflected by the base in a direction such that they then travel back towards the lamp. These rays are then absorbed, and/or wholly or partly diverted by total reflection, on the bulb of the lamp, so that they once again leave the headlight in the form of parasitic radiation which alters the quality of the overall beam. In particular, in the case where the headlight is intended to produce a cut-off beam, such as a dipped beam or fog penetrating beam, these diverted rays can leave the headlight in an upward direction, and give rise to dazzling of the drivers of vehicles traveling in the opposite direction.
One known solution to this problem consists in designing the direct light trap or mask, which is usually provided in front of the lamp in order to intercept the radiation emitted by the light source directly towards the cover glass, so that it will also intercept this parasitic radiation. However, this solution has a disadvantage in that this light is then lost. In addition, some of the light reflected from the base of the reflector does in fact once again reach the light source and is absorbed by it. This can increase the working temperature of the light source, and therefore reduce its useful life. This problem can be made worse by heating of the direct light mask due to absorption of the intercepted radiation.
In addition, an arrangement in which the base of the reflector is masked, or indeed made non-reflective, will not be any more satisfactory. In this connection, it could be ugly from the aesthetic point of view when the headlight is extinguished, and could make it more complicated to manufacture. In addition, a not insignificant quantity of light will then be lost, and its absorption by the reflector will tend to give rise to undesirable heating of the reflector.
An object of the present invention is therefore to overcome the above mentioned limitations in the state of the art, and to propose a headlight in which the base region of the reflector is able to be used for playing a useful part in producing the headlight beam.
Another object of the present invention is to make use of the base zone to increase the thickness of the beam, especially where the light source is oriented in a horizontal direction at right angles to the optical axis, which in itself gives rise to risks of producing a beam which is too thin.
According to the invention, a motor vehicle headlight including a light source cooperating with a reflector to form a light beam, the reflector having an active base region situated immediately behind the light source, and the reflector being adapted to reflect the radiation produced by the light source so as to generate a beam of given photometry, is characterised in that the said base region includes, in at least one zone which, in order to satisfy the required photometry, is adapted to reflect the radiation from the light source into the close vicinity of the latter, a corrected reflective surface which is adapted to produce, from the light source, a corrected reflected radiation which remains spaced away from the said close vicinity without disturbing the photometry of the beam.
The corrected reflected radiation is preferably propagated outside a bulb surrounding the light source.
Preferably, the light source extends substantially horizontally and transversely to an optical axis of the reflector; the reflector is constructed, at least in its central region, from a vertical generatrix which is adapted to align substantially all of the images of the light source below a cut-off line; in that the said corrected reflective surface occupies a zone of the reflector which is low in height and which is located substantially at the same level as the light source, the corrected reflective surface having a corrected vertical generatrix such that the corrected reflected radiation is substantially spaced away from the horizon in the vertical direction.
Preferably in that case, at least part of the corrected reflected radiation is directed downwards towards the road, and is adapted so that it directly completes the light beam formed by the reflector while increasing its downward thickness.
In another version, at least part of the corrected reflected radiation is diverted downwards towards a lower region of the reflector, and is adapted so that, after being reflected by the said lower region, it completes the light beam which is formed by the said reflector while increasing the downward thickness of the latter.
In a further version, at least part of the corrected reflected radiation is redirected upwardly towards a region of the solid angle defined in space in front of the vehicle that corresponds to the position of gantry-mounted road signs with respect to the road.
Preferably, the reflector includes first and second zones, having a first and a second corrected reflective surface respectively and lying, respectively, immediately above and below a horizontal plane downwardly tangential to the light source.
Preferably in that case, the first corrected reflective surface redirects the light downwards towards the reflector, and the second corrected reflective surface redirects the light downwards towards the road; and/or the first corrected reflective surface redirects the light upwardly towards a region corresponding to gantry-mounted road signs, while the corrected reflective surface redirects the light downwards towards the road.
Preferably, at least one of the following features is present, to the extent that they are compatible:
the said corrected reflective surface, or at least one-said surface, has an essentially rectilinear vertical generatrix;
the said corrected reflective surface, or at least one said surface, has a curved vertical generatrix;
the said corrected reflective surface, or at least one said surface, has a vertical generatrix which is joined without change of slope to at least one other part of the reflector.
Preferably, the corrected reflective surface, or at least one said surface, has a substantially constant height of between 2 and 6 mm.
Preferably, the corrected reflective surface, or at least one said surface, extends over the whole width of the reflector.
Preferably, the corrected reflective surface, or at least one said surface extends over part of the width of the reflector covering at least one region situated immediately behind the light source.
Further features, objects and advantages of the present invention will appear more clearly on a reading of the following detailed description of some preferred embodiments of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.